DE1552981A1 - Connection of metallic elements - Google Patents

Description

Patents, II notification

the

Switches Incorporated, = 317 East Ontario Street,

ÖMcago / lllinois (Y.St .A.)

relating to the connection of metallic elements

The invention relates generally to the manufacture of composite articles from metallic elements, especially on the connection of light metals such as aluminum with other metallic materials. In detail it concerns a new and innovative process for resistance welding of aluminum wire with elements of zinc.

The articles produced according to the invention are composite articles made of metallic elements which are connected to one another by welding, in particular resistance welding. The method includes preferably heating the higher melting point material to a temperature such that at Touching the higher melting object with the other, a relatively cool metallic object

BADORiGiNAL 909882/0018

localized melting takes place in the contact area, whereupon a mechanical pressure is exerted so that the lower melting metal is displaced by moving around the edge of the higher melting material (e.g. a Aluminum wire) that flows to the desired depth of penetration is brought into the lower melting metallic material.

Light materials such as aluminum, for example in wire form, are known to have good electrical conductivity and high strength combined with low weight. However, occur when joining aluminum with other materials present numerous difficulties. Due to the impossibility of using the usual soldering methods, in particular with resinous fluxes and soft solder to be used to join aluminum wire, it became more extensive Practically prevented the use of aluminum in areas where its use would be beneficial. Heine's zinc is generally considered to be the most corrosion-resistant solder for joining aluminum! however, it was because of its poor flow properties not yet in a major way Scope applied. Another process known as brazing aluminum uses temperatures required that are so close to the melting point of the aluminum that one can produce consistent results required regulation is almost impossible. If electrical conductors continue to come into contact with other conductor values

909882/0916 ^BAD ORIGINAL

materials, then there generally follows a constant ίτΛ impermissible increase in the electrical resistance at the contact surface,

Further difficulties in "this area are the defects of the connecting points to be formed between aluminum wire and elements aas other metals, ζ .B * Connection connections from lapfer _a The aluminum oxide adheres very firmly to the surface of the aluminum wire and becomes part of the joint of the TerMadimgszone If the connection is not made by melting ropes of the elements, but only by crimping, then there is a paste to prevent the formation of oxide in the folded connection necessary »to prevent the formation of resistance layers of aluminum oxide on the metal boundary surfaces.

In addition to the difficulties "in forming a good connection between the JHnminiumdraht an element IMD of another metal, difficulties due to galvanic corrosion because a IPotentialdifferenz between the aluminum and AEEN element from the other metal processing can take st ·

Numerous efforts have already been made to this

909882/0316

To "eliminate" disadvantages, for example by adding a composite "block, "For example from copper, around an aluminum core was cast) by" plating "freshly cleaned Aluminum wire with a zinc layer, with the aim of simplifying the subsequent soldering, which is often done in was carried out in an inert atmosphere, with the plating to prevent the formation of an aluminum oxide layer? by rubbing the surface of the aluminum with the aluminum immersed in molten zinc, etc.

A process has now been developed for the production of metallic composite objects from several components.

at least winds, which has particular advantages when] a component is a light metal that forms firmly adhering stable oxide layers, the composite objects being practical do not have a voltage gradient across the connection point, which greatly reduces galvanic corrosion and connection points are formed with relatively high tensile strength. In a special embodiment of the composite objects, when aluminum wire is connected to a zinc element, the composite objects are still next to it practically free from thermal stress, as the expansion coefficients of these metals are similar.

The method of making these composite articles is to have a higher melting point metallic

909882/0918

Brings solid body into surface contact with a lower melting point metal object, the contact area between the higher melting metallic solid • and the lower melting metal object makes up a small proportion of the area of the latter, the higher-melting metallic plague body to one Temperature in the range between the melting points "of both metals heated on the metal object in the direction in which the contact is forced, a mechanical pressure is exerted and the pressure is kept right. This causes the heated part of the metal object with a higher melting point a melting of the zone of the one in contact with it, lower melting metal as well as a displacement of the molten part of the lower melting metal object. The heating is then discontinued while pressure is maintained on the metals until they do have cooled down so that the molten, lower melting metal solidifies and the higher melting metal metallic solid in the embedded layer.

As below using aluminum wire as a representative of metals, which normally have a firmly adhering surface layer of metal oxide, as well as one Zinc connecting element is explained, the preferred method is that one of the aluminum wire, i.e. the higher melting point material, preferably on a Heated temperature higher than the melting point of the

909 8 8 2/091 p.

Zinc lies while the two metals are right with one another are in contact, the hot aluminum wire, for example by forging, presses into the zinc element, wherein the hot aluminum wire displaces the molten zinc in the contact zone due to the forging pressure. Then it will be the composite is cooled so that the molten zinc solidifies and the aluminum wire is in the position he has penetrated the zinc element.

The composite wire articles obtained in accordance with the present invention can be viewed as two or more metallic elements that are connected to one another in such a way that they can be used in an electrical circuit. These composite articles can take many forms, e.g. as electrical conductors connected to a lower melting metal connector, e.g. the shape of an aluminum wire connected with zinc connectors, an aluminum wire, which is connected to an aluminum wire via a zinc connection, an aluminum wire which is connected via a zinc connection connected with a copper wire, as well as the form, of tantalum connected with copper wire, of Magnesium, which is bonded to a zinc plate, continues the shape with three metallic elements, each being Element associated with a lower melting element, etc. The nature of a composite article with a newly found one Applicability is an aluminum wire with a zinc connector that acts as an electrical connection for a starter winding is suitable. The composite articles have surprising properties, 909882/0 916

only when the manufacturing technique is perfected recognized. Mention should be made here of a strong connection with a greater tensile strength than the aluminum wire itself, a low electrical resistance, no risk of the connection due to thermal stresses breaks * and a low contact potential, i.e. none Significant galvanic corrosion, through which the more electropositive metal consumes itself in normal operation.

The low contact potential of a composite article according to the invention, e.g. unusual. When measuring according to the usual contact potential method an aluminum-zinc compound shows a work potential between zinc and aluminum of 3.4-0 minus 3 "38" i.e. 0.02 volts compared to one normal work potential between zinc and copper of 1.67 volts. This distinctive difference was due to the work potential, which results from the electrical voltage

row in which the potential difference between aluminum and zinc or between aluminum and copper are relatively high, cannot be foreseen. The potential difference between aluminum and zinc is 0.9 volts, and that between aluminum and copper is even more higher.

Generally, one embodiment of the composite article of the invention made as follows}

909882/0918

For example, a wire and a lower melting point metallic element are used in the holder of an AC resistance welder with an upper electrode mechanism with low inertia and good welding speed on top of each other. This device is intended to be used with appropriate heat and welding cycle control be provided. One such device is, for example, the "Taylor Winfield EB1" welder with a 5 kilowatt transformer and a synchronous precision heat regulator.

The wire to be heated is brought into contact with a tungsten resistance electrode, whereby the wire is heated preferentially. The lower-melting element is brought into contact with an electrode with high conductivity, for example made of copper, so that the electrical conductivity is high and the electric current can 'be' passed through without the lower-melting element suffering a significant increase in temperature. The wire to a temperature in the range between the melting points of the metals, ie zinc and aluminum between about 4I9 ⁰ C and about 659 ⁰ C, preferably between about 625 ⁰ C

and 5OO ⁰ C is heated, a pressure is applied to the wire so that it comes with the lower-melting metal element in contact with and is pressed into the element, will be displaced whereby the molten metal in the contact zone.

909882/0918

The "preferred heating of the higher melting point metal to a temperature above the melting point of the metal with which it is to be bonded is determined by the type and the construction of the contact electrode for the metals to be connected as well as the direction of current "influenced Local heating can be achieved with the help of a Y / resistance electrode, e.g. an electrode made of a tungsten-copper alloy,

Electricity can be achieved. The heating increases when the from

the electrode flows into the workpiece.

There is a resistance electrode with the higher melting point Metal and a highly conductive electrode in contact with the metallic element with the lower melting point, is "preferred, i.e. localized, the higher melting point Metal heats up, while the metallic clement with the lower melting point remains relatively cool, except in the zone in which there is direct contact between the two metals.

If the higher melting metal reaches a temperature that higher than the melting point of the other metal thing is quickly the case with the help of a resistance welding device, the metallic element melts with the lower melting point in a localized zone. This applies to the object with the higher melting point if pressure is exerted, it displaces the metal.

909882/0918

The mechanical pressure to achieve this hot deformation can be exercised through the electrodes. This can be done in different ways, i.e. by spring pressure or pneumatis Shem or hydraulic way. In general, devices that are capable of stamping pressures are in the range exercise from approximately 22.7 "to 204 kg (50" to 450 lbs), sufficient for most purposes. For hot forming of Zinc and aluminum elements will suffice with punch pressures in the range of approximately 34 "to 68 kg (75" to 150 rbs).

After the higher melting point metal has been pressed into the lower melting point metallic element, to be there To displace a localized molten zone, the molten zone must solidify again, so that the higher melting zone Ketall is held in place "before pressure is relieved when a tight connection is made should be guaranteed. Ss is usually sufficient if you let the "touching" letters every few seconds after switching off the electric current in the atmosphere allowed to cool, whereupon the composite article removed from the welding device.

According to a further embodiment of the invention can a copper wire and a welding eyelet or a cable lug (welding leeg) made of a lower, melting!.! metal are placed on top of each other in a folding machine, whereupon the Cse or the cable lug is folded and folded over so that

909882/0916

the wire is held in the taIz. Such a fold can before heating by mechanical deformation or during of heating with the help of the electrode pressure.

The heating required for this embodiment of the invention uses an AC spot welder with an upper slectrode mechanism with low inertia modified so that both electrodes vResistance electrodes are.

If the electrodes touch the crimped cable lug, with the wire held in the fold, the welding streaks switched on, the wire is due to its higher, due to the smaller cross-section, Resistance heated quickly. The current goes without a noticeable rise in temperature of the lower melting metal Element through this. The U-shaped cable lug does not de-energize the welded connection, for example if the cable lug is made of metallic zinc and the Wire is made of aluminum because the specific resistance of zinc compared to good conductors such as copper is low and the specific conductivity of aluminum is much higher than that of zinc, so that the greater part of the Welding current goes through the aluminum.

After the wire has been heated to a temperature in the range between the melting points of the metals, ie in the case of zinc and aluminum between about 4-19 and 659 ⁰ O, the

BAD ORIGINAL 9 0 9 882/0916

U-shaped cable lug exerted a pressure so that the opposing surfaces of the cable lug are pressed closer together. As soon as the legs of the U-shaped cable lug come into contact with the heated wire above the melting point of the cable lug metal, localized melting occurs on the contact surfaces. The applied pressure displaces the molten metal and the resistance to the closing of the gap between the legs of the U-shaped cable lug is removed. After the higher melting metal object deeply in both legs of the U-shaped cable shoe has penetrated relatively, the melt zone is abgekuhlf, whereby ^s aer noherschmelzende · metal object in place is maintained.

According to this embodiment of the invention, a ' bond with improved mechanical strength obtained. A wire holder is obtained for application forms that Are exposed to vibrations or shocks.

The invention is explained in more detail by means of the following examples, which are not intended to restrict the invention.

909882/0916

example 1

When welding an aluminum wire "EC No. 15" & it ' one about 25 mm long and about 6.3 mm (1/4 inch) "wide Zinc plate about 1.3 now (0.05 inch) thick a 6.3 mm long aluminum wire insulated with aluminum is brought into contact with the plate. A tungsten resistance heating electrode (Mallory 100W) with the stripped aluminum wire on the surface that is the contact surface with the zinc plate opposite, brought into contact. The tungsten electrode is spring loaded and a mechanical pressure of approximately 53 kg (125 lbs) is applied.

The zinc plate rests on a button electrode made of Zupfer (Mallory 1QW3) in the lower electrode holder. Is passed by means of this device current, the aluminum wire is rapidly heated to a peak temperature of about 600 ⁰ C. Under these temperature and pressure conditions, the zinc melts in contact with the hot aluminum wire and the aluminum difVa / t displaces the molten material so that the zinc flows out around the wire and carries with it at least some of the aluminum oxide on the surface of the wire. By switching off the current or in some other suitable way, for example by changing the current direction, etc., the heating is stopped, and when it cools the aluminum wire rests firmly in the embedded position.

909882/0916

The tensile strength of the connection formed according to Example 1 (as determined by axial pull) is generally about 11.4 to 12.6 kg (25 to 28 lbs).

The fatigue strength of the joint according to Example 1 was determined by thermal cycling tests, ie the composite article was heated by passing electrical current, while the surrounding area has been maintained at various temperatures ranging from -75 ° to +350 ⁰ O. Another experiment was carried out at 38 ^° C. in a relative humidity of 95 °.

The current density to achieve the rapid temperature rise was about 77.5 A / mm (50,000 amp. Sq / in.), Where Ohm's law (I R) was used.

The voltage drop (in millivolts) across the connection point was used to control the test. The values were with a full potentiometer at current densities of about 3 »1 A / mm (2000 amp / sq.inch). The duration of a period was 1 minute total with power on for 2 seconds. Each attempt was repeated 150,000 times. In none of the above tests indicated a failure of the connection due to increased contact resistance established.

909882/0916

Example 2

When welding an aluminum wire "BC No.15" and an aluminum wire "EO No.12" with a zinc element with an eyelet about 13 mm (1/2 inch) long, 9.5 mm (3 / sf wide, and about 1.6 mm (1/16 inch) thick) are stripped wire pieces of about 9.5mm each (3/8 inch) length brought into contact with the eyelet.

About 9.5 mm of the eyelet are folded over and firmly attached to the the two pieces of wire jammed, as a result of which they are held in place between the two legs of the U-shaped eyelet will.

Then an upper and a lower resistance welding electrode (Mallory 10W3) brought into contact with the legs Φr U-shaped eyelet, and it becomes a mechanical Pressure of about 68 kg applied.

When the current is passed from the electrodes through the two legs of the Zinköse and the wires in the rebate, the aluminum wire is rapidly heated to a temperature of about 58o ⁰ G. Under these conditions of temperature and pressure, the zinc melts on the surfaces in contact with the hot aluminum wires, thereby eliminating the resistance to closing the gap between the two legs of the loop. With the Druok applied, the distance between the two decreases

90988 2/0916

Legs of the eyelet to "for example about 0.4 mm, i. to a distance that is less than the diameter of the aluminum wires.

When the distance between the legs of the eyelet is shortened, the zinc melts on the hot aluminum wires contacting surfaces, and the aluminum wires displace the molten material, so that the Zinc flows around every wire. When the power is turned off, the composite cools down, and both aluminum wires are held in the embedded position.

The tensile strength of the connection point formed according to this example (determined by axial pulling) can be in Range between approximately 13 »6 and 15» 9 kg (30-35 lbs.),

The foregoing general description is only intended to provide a clearer understanding of the invention? No unnecessary restrictions should be inferred, since changes can readily be made by those skilled in the art.

- Claims «-

909882/0915

Claims (8)

Claims j 1. A method for joining solid metal objects with different melting points, characterized in that one has a higher melting point. metallic, solid object with a relatively small surface area with a lower melting metal object with a relatively large surface in contact. brings the higher melting metal object heated to a temperature in the range between the melting points of the two metals, a mechanical pressure on the heated part of the higher melting metal object in a direction in which a contact of the two metal objects is forced, exerts and maintains the pressure, whereby the heated part of the higher melting point metal object causes melting of the contact surface with the lower melting point metal and the molten part of the lower melting point metal in the contact zone displaced, whereupon the heating is interrupted while maintaining the pressure until the objects have cooled and the molten _/ lower melting metal has solidified, whereby the higher melting metal object in and a metal object is embedded and held in place./ 909882/0918 2. The method according to claim 1, characterized in that the heating takes place electrically · and by touch a resistance heating electrode with the part of the higher melting point Metal object that is in contact with the object with the larger surface, while this is in contact with an electrode with high conductivity, is localized. 3. The method according to claim 1 or 2, characterized in that the higher melting metal object, the one relatively small cross-section "has, on a relatively small area of the lower melting point Metal object places, folds parts of this metal object over the first metal object, the first metal object heated to a temperature in the range between the melting points of the two metals, a mechanical one Applying pressure to the outer surfaces of the folded back portions of the second metal object and maintaining the pressure receives so that by touching the first ketal object the part of the second metal object in direct contact with it melts, whereupon the pressure continues to act leaves so that the first metal object displaces the molten part of the second metal object when the opposing surfaces of the folded part of the second metal object are pressed into an age, in which the distance between these surfaces is less than that 909882/0916 Is cross-section of the first metal object, and that the heating is then stopped and the metal objects are cooled to produce the molten, lower melting metal to solidify and to connect the metal objects together. 4. The method according to claim 1 - 3 »characterized in that that the lower melting metal object in independent steps at separate points with connects two metal objects whose melting point is higher than that of the first metal object. 5. The method according to claim 4, characterized in that a connecting piece is used as the lower melting metal object made of zinc and, as objects with a higher melting point, an aluminum wire and a copper wire used. 6. The method according to claim 1-3 »characterized in that there is aluminum as the higher-melting metal and as lower melting metal zinc is used. 7. The method according to claim 5 or 6, characterized in that that nan exerts a mechanical pressure of about 34 to 68 kg. 8. The method according to claim 5 »6 .or 7, characterized in that the aluminum at about 500 - heated 625 ⁰ C. 80988 2/0916